[chromedriver] Use nodeType instead of instanceof.

For some reason, some pages redefine window.Element, which breaks our previous
use of instanceof.

BUG=chromedriver:1388

Review-Url: https://codereview.chromium.org/2620803002
Cr-Commit-Position: refs/heads/master@{#443405}

chrome/test/chromedriver/js/call_function.js

@@ -260,7 +260,8 @@ function wrap(value) {
   // frames[0].document.body instanceof Object == false even though
   // typeof(frames[0].document.body) == 'object'.
   if ((typeof(value) == 'object' && value != null) ||
-      (typeof(value) == 'function' && value instanceof Element)) {
+      (typeof(value) == 'function' && value.nodeName &&
+       value.nodeType == Node.ELEMENT_NODE)) {
     var nodeType = value['nodeType'];
     if (nodeType == NodeType.ELEMENT || nodeType == NodeType.DOCUMENT
         || (SHADOW_DOM_ENABLED && value instanceof ShadowRoot)) {

chrome/test/chromedriver/test/run_py_tests.py

@@ -1378,6 +1378,13 @@ class ChromeDriverTest(ChromeDriverBaseTestWithWebServer):
     if (self._driver.w3c_compliant):
       self.assertEquals(len(element._id), w3c_id_length)
 
+  def testFindElementWhenElementIsOverridden(self):
+    self._driver.Load('about:blank')
+    self._driver.ExecuteScript(
+        'document.body.appendChild(document.createElement("a"));')
+    self._driver.ExecuteScript('window.Element = {}')
+    self.assertEquals(1, len(self._driver.FindElements('tag name', 'a')))
+
 
 class ChromeDriverPageLoadTimeoutTest(ChromeDriverBaseTestWithWebServer):